(1) Field of the Invention
The present invention relates to telephone line circuits and more particularly to a circuit which can perform the full range of line supervision functions.
(2) Description of the Prior Art
The use of Hall effect devices in line circuits has previously been disclosed in U.S. Pat. No. 4,166,928 issued on Sept. 4, 1979 to R. J. Sabon. However, this circuit is limited to the detection of loop status either during the presence or absence of ringing current.
The Hall effect device, however, can provide an output signal representative of minute variations in loop or line current. Thus its potential for use in monitoring all varieties of line conditions has not been developed. The prior art still uses relay type line circuits to test line conditions such as on-hook leakage current, open circuit ringer test, power cross, and ring ground short. Thus the prior art has not been able to adapt Hall effect devices to the full range of line supervision functions.
Accordingly, it is the object of the present invention to provide a novel line circuit, utilizing a single Hall effect device to perform the full range of line supervision functions.